arch/openrisc/mm/fault.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * OpenRISC fault.c
   4  *
   5  * Linux architectural port borrowing liberally from similar works of
   6  * others.  All original copyrights apply as per the original source
   7  * declaration.
   8  *
   9  * Modifications for the OpenRISC architecture:
  10  * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
  11  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
  12  */
  13
  14 #include <linux/mm.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/extable.h>
  17 #include <linux/sched/signal.h>
  18 #include <linux/perf_event.h>
  19
  20 #include <linux/uaccess.h>
  21 #include <asm/bug.h>
  22 #include <asm/mmu_context.h>
  23 #include <asm/siginfo.h>
  24 #include <asm/signal.h>
  25
  26 #define NUM_TLB_ENTRIES 64
  27 #define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1))
  28
  29 /* __PHX__ :: - check the vmalloc_fault in do_page_fault()
  30  *            - also look into include/asm/mmu_context.h
  31  */
  32 volatile pgd_t *current_pgd[NR_CPUS];
  33
  34 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
  35                               unsigned long vector, int write_acc);
  36
  37 /*
  38  * This routine handles page faults.  It determines the address,
  39  * and the problem, and then passes it off to one of the appropriate
  40  * routines.
  41  *
  42  * If this routine detects a bad access, it returns 1, otherwise it
  43  * returns 0.
  44  */
  45
  46 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
  47                               unsigned long vector, int write_acc)
  48 {
  49         struct task_struct *tsk;
  50         struct mm_struct *mm;
  51         struct vm_area_struct *vma;
  52         int si_code;
  53         vm_fault_t fault;
  54         unsigned int flags = FAULT_FLAG_DEFAULT;
  55
  56         tsk = current;
  57
  58         /*
  59          * We fault-in kernel-space virtual memory on-demand. The
  60          * 'reference' page table is init_mm.pgd.
  61          *
  62          * NOTE! We MUST NOT take any locks for this case. We may
  63          * be in an interrupt or a critical region, and should
  64          * only copy the information from the master page table,
  65          * nothing more.
  66          *
  67          * NOTE2: This is done so that, when updating the vmalloc
  68          * mappings we don't have to walk all processes pgdirs and
  69          * add the high mappings all at once. Instead we do it as they
  70          * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
  71          * bit set so sometimes the TLB can use a lingering entry.
  72          *
  73          * This verifies that the fault happens in kernel space
  74          * and that the fault was not a protection error.
  75          */
  76
  77         if (address >= VMALLOC_START &&
  78             (vector != 0x300 && vector != 0x400) &&
  79             !user_mode(regs))
  80                 goto vmalloc_fault;
  81
  82         /* If exceptions were enabled, we can reenable them here */
  83         if (user_mode(regs)) {
  84                 /* Exception was in userspace: reenable interrupts */
  85                 local_irq_enable();
  86                 flags |= FAULT_FLAG_USER;
  87         } else {
  88                 /* If exception was in a syscall, then IRQ's may have
  89                  * been enabled or disabled.  If they were enabled,
  90                  * reenable them.
  91                  */
  92                 if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE))
  93                         local_irq_enable();
  94         }
  95
  96         mm = tsk->mm;
  97         si_code = SEGV_MAPERR;
  98
  99         /*
 100          * If we're in an interrupt or have no user
 101          * context, we must not take the fault..
 102          */
 103
 104         if (in_interrupt() || !mm)
 105                 goto no_context;
 106
 107         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 108
 109 retry:
 110         mmap_read_lock(mm);
 111         vma = find_vma(mm, address);
 112
 113         if (!vma)
 114                 goto bad_area;
 115
 116         if (vma->vm_start <= address)
 117                 goto good_area;
 118
 119         if (!(vma->vm_flags & VM_GROWSDOWN))
 120                 goto bad_area;
 121
 122         if (user_mode(regs)) {
 123                 /*
 124                  * accessing the stack below usp is always a bug.
 125                  * we get page-aligned addresses so we can only check
 126                  * if we're within a page from usp, but that might be
 127                  * enough to catch brutal errors at least.
 128                  */
 129                 if (address + PAGE_SIZE < regs->sp)
 130                         goto bad_area;
 131         }
 132         vma = expand_stack(mm, address);
 133         if (!vma)
 134                 goto bad_area_nosemaphore;
 135
 136         /*
 137          * Ok, we have a good vm_area for this memory access, so
 138          * we can handle it..
 139          */
 140
 141 good_area:
 142         si_code = SEGV_ACCERR;
 143
 144         /* first do some preliminary protection checks */
 145
 146         if (write_acc) {
 147                 if (!(vma->vm_flags & VM_WRITE))
 148                         goto bad_area;
 149                 flags |= FAULT_FLAG_WRITE;
 150         } else {
 151                 /* not present */
 152                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 153                         goto bad_area;
 154         }
 155
 156         /* are we trying to execute nonexecutable area */
 157         if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC))
 158                 goto bad_area;
 159
 160         /*
 161          * If for any reason at all we couldn't handle the fault,
 162          * make sure we exit gracefully rather than endlessly redo
 163          * the fault.
 164          */
 165
 166         fault = handle_mm_fault(vma, address, flags, regs);
 167
 168         if (fault_signal_pending(fault, regs)) {
 169                 if (!user_mode(regs))
 170                         goto no_context;
 171                 return;
 172         }
 173
 174         /* The fault is fully completed (including releasing mmap lock) */
 175         if (fault & VM_FAULT_COMPLETED)
 176                 return;
 177
 178         if (unlikely(fault & VM_FAULT_ERROR)) {
 179                 if (fault & VM_FAULT_OOM)
 180                         goto out_of_memory;
 181                 else if (fault & VM_FAULT_SIGSEGV)
 182                         goto bad_area;
 183                 else if (fault & VM_FAULT_SIGBUS)
 184                         goto do_sigbus;
 185                 BUG();
 186         }
 187
 188         /*RGD modeled on Cris */
 189         if (fault & VM_FAULT_RETRY) {
 190                 flags |= FAULT_FLAG_TRIED;
 191
 192                 /* No need to mmap_read_unlock(mm) as we would
 193                  * have already released it in __lock_page_or_retry
 194                  * in mm/filemap.c.
 195                  */
 196
 197                 goto retry;
 198         }
 199
 200         mmap_read_unlock(mm);
 201         return;
 202
 203         /*
 204          * Something tried to access memory that isn't in our memory map..
 205          * Fix it, but check if it's kernel or user first..
 206          */
 207
 208 bad_area:
 209         mmap_read_unlock(mm);
 210
 211 bad_area_nosemaphore:
 212
 213         /* User mode accesses just cause a SIGSEGV */
 214
 215         if (user_mode(regs)) {
 216                 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
 217                 return;
 218         }
 219
 220 no_context:
 221
 222         /* Are we prepared to handle this kernel fault?
 223          *
 224          * (The kernel has valid exception-points in the source
 225          *  when it acesses user-memory. When it fails in one
 226          *  of those points, we find it in a table and do a jump
 227          *  to some fixup code that loads an appropriate error
 228          *  code)
 229          */
 230
 231         {
 232                 const struct exception_table_entry *entry;
 233
 234                 if ((entry = search_exception_tables(regs->pc)) != NULL) {
 235                         /* Adjust the instruction pointer in the stackframe */
 236                         regs->pc = entry->fixup;
 237                         return;
 238                 }
 239         }
 240
 241         /*
 242          * Oops. The kernel tried to access some bad page. We'll have to
 243          * terminate things with extreme prejudice.
 244          */
 245
 246         if ((unsigned long)(address) < PAGE_SIZE)
 247                 printk(KERN_ALERT
 248                        "Unable to handle kernel NULL pointer dereference");
 249         else
 250                 printk(KERN_ALERT "Unable to handle kernel access");
 251         printk(" at virtual address 0x%08lx\n", address);
 252
 253         die("Oops", regs, write_acc);
 254
 255         /*
 256          * We ran out of memory, or some other thing happened to us that made
 257          * us unable to handle the page fault gracefully.
 258          */
 259
 260 out_of_memory:
 261         mmap_read_unlock(mm);
 262         if (!user_mode(regs))
 263                 goto no_context;
 264         pagefault_out_of_memory();
 265         return;
 266
 267 do_sigbus:
 268         mmap_read_unlock(mm);
 269
 270         /*
 271          * Send a sigbus, regardless of whether we were in kernel
 272          * or user mode.
 273          */
 274         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
 275
 276         /* Kernel mode? Handle exceptions or die */
 277         if (!user_mode(regs))
 278                 goto no_context;
 279         return;
 280
 281 vmalloc_fault:
 282         {
 283                 /*
 284                  * Synchronize this task's top level page-table
 285                  * with the 'reference' page table.
 286                  *
 287                  * Use current_pgd instead of tsk->active_mm->pgd
 288                  * since the latter might be unavailable if this
 289                  * code is executed in a misfortunately run irq
 290                  * (like inside schedule() between switch_mm and
 291                  *  switch_to...).
 292                  */
 293
 294                 int offset = pgd_index(address);
 295                 pgd_t *pgd, *pgd_k;
 296                 p4d_t *p4d, *p4d_k;
 297                 pud_t *pud, *pud_k;
 298                 pmd_t *pmd, *pmd_k;
 299                 pte_t *pte_k;
 300
 301 /*
 302                 phx_warn("do_page_fault(): vmalloc_fault will not work, "
 303                          "since current_pgd assign a proper value somewhere\n"
 304                          "anyhow we don't need this at the moment\n");
 305
 306                 phx_mmu("vmalloc_fault");
 307 */
 308                 pgd = (pgd_t *)current_pgd[smp_processor_id()] + offset;
 309                 pgd_k = init_mm.pgd + offset;
 310
 311                 /* Since we're two-level, we don't need to do both
 312                  * set_pgd and set_pmd (they do the same thing). If
 313                  * we go three-level at some point, do the right thing
 314                  * with pgd_present and set_pgd here.
 315                  *
 316                  * Also, since the vmalloc area is global, we don't
 317                  * need to copy individual PTE's, it is enough to
 318                  * copy the pgd pointer into the pte page of the
 319                  * root task. If that is there, we'll find our pte if
 320                  * it exists.
 321                  */
 322
 323                 p4d = p4d_offset(pgd, address);
 324                 p4d_k = p4d_offset(pgd_k, address);
 325                 if (!p4d_present(*p4d_k))
 326                         goto no_context;
 327
 328                 pud = pud_offset(p4d, address);
 329                 pud_k = pud_offset(p4d_k, address);
 330                 if (!pud_present(*pud_k))
 331                         goto no_context;
 332
 333                 pmd = pmd_offset(pud, address);
 334                 pmd_k = pmd_offset(pud_k, address);
 335
 336                 if (!pmd_present(*pmd_k))
 337                         goto bad_area_nosemaphore;
 338
 339                 set_pmd(pmd, *pmd_k);
 340
 341                 /* Make sure the actual PTE exists as well to
 342                  * catch kernel vmalloc-area accesses to non-mapped
 343                  * addresses. If we don't do this, this will just
 344                  * silently loop forever.
 345                  */
 346
 347                 pte_k = pte_offset_kernel(pmd_k, address);
 348                 if (!pte_present(*pte_k))
 349                         goto no_context;
 350
 351                 return;
 352         }
 353 }